A. Introduction
The mixer assembly of the invention is particularly suitable for use in mixing samples for testing in an electrostatic coalescer test unit. Full scale electrostatic coalescers are used for crude oil dehydration in both Production and Refining. These devices enhance the coalescence of water droplets by the use of an applied electric field. In a strong electric field, water droplets have an induced dipole and are deformed into an ellipsoidal shape. Attraction between the positive and negative ends of adjacent water droplets is a driving force for coalescence. Distortion of the stabilizing emulsifier film (solids, surfactants, asphaltenes, and other compounds) surrounding the water droplets also assists in droplet coalescence.
Chemical additives, such as demulsifiers and solids-wetting agents, are often used in conjunction with applied electric fields for crude oil dehydration. These additives function to destabilize the emulsifier film surrounding the water droplets. Portable batch electrostatic coalescers are used by chemical vendors to conduct quick screening tests for selecting the best chemical additive package for a given crude oil/brine system. These experiments rank order the relative performance of different additive packages and approximate their performance in commercial-scale electrostatic coalescers.
B. Known Devices
InterAv markets a commercially available electrostatic coalescer. Petrolite & Betz have built portable electrostatic coalescers in-house. The InterAv device uses an electrode configuration which is susceptible to electrical shorting when the water concentration gets too high, since both electrodes are immersed in the sample. In the InterAv electrostatic coalescer, there is no means for mixing the sample directly in the tube which is used in the electrostatic coalescer. Demulsifier additives for use in electrostatic coalescers are conventional and many varieties of demulsifiers are commercially available from vendors such as Petrolite and Betz.